fix(producer): dedupe local font embedding by resolved path

[miguel-heygen]

Summary

• cache embedded local fonts by resolved absolute path
• reuse one data URI across equivalent sub-composition-relative aliases
• add regression coverage for repeated references to one font file

Reproduction

A composition with three @font-face URLs (assets/shared.woff2, ./assets/shared.woff2, and assets/../assets/shared.woff2) triggered three embed operations before this change. With large TTC assets across sub-compositions, that repeated read/compression caused multi-minute compile stalls.

Verification

• bun test packages/producer/src/services/htmlCompiler.test.ts (103 pass)
• bun run --cwd packages/producer typecheck
• bunx oxfmt --check packages/producer/src/services/htmlCompiler.ts packages/producer/src/services/htmlCompiler.test.ts
• pre-commit hooks passed (lint, format, fallow, typecheck)